Engines, including diesel engines, gasoline engines, gaseous fuel powered engines, and other engines known in the art exhaust a complex mixture of air pollutants. These air pollutants include solid material known as particulate matter or soot. Due to increased attention on the environment, exhaust emission standards have become more stringent, and the amount of particulate matter emitted from an engine is regulated depending on the type of engine, size of engine, and/or class of engine.
One method implemented by engine manufacturers to comply with the regulation of particulate matter exhausted to the environment has been to remove the particulate matter from the exhaust flow of an engine with a device called a particulate trap. A particulate trap is a filter designed to trap particulate matter and typically consists of a wire mesh or ceramic honeycomb medium. However, the use of the particulate trap for extended periods of time may cause the particulate matter to build up in the medium, thereby reducing the functionality of the filter and subsequent engine performance.
The collected particulate matter may be removed from the filter through a process called regeneration. To initiate regeneration of the filter, the temperature of the particulate matter entrained within the filter must be elevated to a combustion threshold at which the particulate matter is burned away. One way to elevate the temperature of the particulate matter is to inject a catalyst such as diesel fuel into the exhaust flow of the engine and ignite the injected fuel. Another way is to use a heating element or a flame-producing burner to heat the filter to the combustion threshold.
One method of controlling regeneration is described in U.S. Patent Application Publication No. 2005/0241301 by Okugawa et al. published on Nov. 3, 2005 (the “301 publication”). The 301 publication discloses a system to control regeneration of a diesel particulate trap (DPF) within an exhaust flow path. The system includes a temperature sensor upstream of the DPF, a temperature sensor downstream of the DPF, and a DPF differential pressure sensor in communication with a controller. As particulate matter accumulates in the DPF, the upstream-downstream pressure difference increases. The controller estimates the amount of accumulation based on the pressure difference and determines a target temperature necessary for regeneration of the DPF based on the amount of accumulation. During subsequent DPF regeneration, the controller operates an upstream oxidation catalyst to heat the DPF to the target temperature and thereby combust all of the accumulated particulate matter.
Although the system of the '301 publication may heat the DPF to an appropriate target combustion temperature, it may malfunction under some circumstances. Specifically, the system uses the upstream temperature sensor to determine the temperature of the DPF during regeneration. Thus, if the upstream temperature sensor and the downstream temperature sensor are installed in the wrong positions (i.e., swapped) due to improper manufacture or assembly, the system may improperly control regeneration. For example, the system may heat the DPF to a temperature far beyond the target and/or for a longer period of time than necessary, causing damage thereto or failure thereof.
This disclosure is directed to overcoming one or more of the problems set forth above.